SilentScope - Can't really emulate that eyepiece view, and it's impossible without it.
Crossbow - Yeah, you can play it with a mouse or a lightgun.. but it's just not the same as sighting down that crossbow...
Boot Hill - it's emulated, but the plain old b&w pixels are boring as heck. It's unbelievable how much difference the artwork and the mirror setup in the real cab makes.
Street Fighter (not Street Fighter II, the original) - Can't emulate those pneumatic pushbuttons.
Holoseum - can't emulate that display.